# An important feature of tablets is battery life, the number of hours before the battery needs to be recharged.

2341 Views

An important feature of tablets is battery life, the number of hours before the battery needs to be recharged. The data shown in the table below contain the battery life of 10 WiFi-only and 10 3G/4G/WiFi 9- through 12-inch tablets. Complete parts (a) through (C).

 WiFi Only 3G/4G/WiFi 44 29 34 36 44 42 20 31 56 52 61 52 52 59 56  23 40 33 45 60

a. Assuming that the population variances from both types of tablets are equal, is there evidence of a difference in the mean battery life between the two types of tablets? Use a=0.01.

Let u, be the mean battery life for WiFi-only tablets and be the mean battery life for 3G/4G/WiFi tablets. There are different applications that you can use to calculate the sample statistics,

WiFi only

mean = 38.8

Standard deviation = 10.932

4G/WiFi

Mean = 48.1

Standard deviation = 12.706

Use statistics from your samples and replace in the formulas below.

Pooled standard deviation calculation,

s^2  = (n1-1 * s1^2   + n2-1 * s2^2)/(n1 + n2  - 2)

s^2  = (n1-1 * s1^2   + n2-1 * s2^2)/(n1 + n2  - 2)

s^2  = (9 * 10.932^2 + 9 * 12.706^2)/(10+10-2)

s^2 = 140.48

t statistic  = (38.8 - 48.1)/sqrt(140.48 * (1/10 + 1/10)) = -1.755

pooled variances used, Calculate critical value in Excel using Excel function, at an alpha of 0.01, =T.INV.2T(0.01,18) =  2.878 or -2.878

Reject the null hypothesis if the absolute value of the test statistic is greater than the critical value calculated.

Results found present insufficient evidence against the null hypothesis at the 5% level of significance.